An assesment of porosity and pore sizes in hardened cement pastes

The porosity of hardened cement paste was analysed using fluid displacement methods, optical, scanning and transmission electron microscopy and mercury intrusion porosimetry. Attention has been drawn to the problems of mercury porosimetry and in particular to the extent of the pore volume which is missed by mercury. Previous workers have assigned the lost porosity to pore sizes too fine to be seen by mercury but this paper considers the contribution of closed pores. Nitrogen and water adsorption studies have been carried out on the pastes to determine qualitatively the magnitude of the pore volume beyond the range of mercury porosimetry. This volume was found to be very small. Emphasis has been placed upon the importance of large spherical pores, which may be missed by mercury porosimetry and adsorption studies, in determining the strength of cement pastes.